1. Field of the Invention
The present invention relates to a handpiece for dental use, and more particularly, to a handpiece to be used by a dentist for cutting or drilling a root canal of a tooth.
2. Description of the Related Art
In forming a root canal of a tooth, a dental reamer or a dental file (hereinafter referred to as xe2x80x9ccutting toolxe2x80x9d) is generally used. The cutting tool may be operated manually or with use of a handpiece with a drive mechanism. With these cutting tools, a spiral cutting edge is inserted into a root canal, and the back and forth movements or rotational movements of the cutting tools by changing the cutting tools corresponding to the shape of the root canal allows the root canal to be tapered. To cut a root canal, a handle of a cutting tool is held for manual operation, or a cutting tool is connected to a dental handpiece for using rotationally driving force of motor or the like.
Since a dental reamer has a large lead, that is, a relatively gentle spiral cutting edge, it is mainly used for cutting by rotational movements. In contrast, a dental file has a spiral cutting edge having a lead smaller than that of the dental reamer, therefore, it is mainly used for cutting through back and forth movements like a file. Further, the dental file is often used by incorporating the back and forth movements as well as some rotational movements at the same time, which allows a root canal to be cut by the back movement and debris generated by the cutting to be carried away to outside of the root canal through spiral channels of the edge portion.
A dental handpiece heretofore in use for operating these cutting tools is sometimes capable of driving the tools both by the back and forth movements and by the rotational movement. xe2x80x9cThe back and forth movementsxe2x80x9d means the movements of the cutting tools for cutting by the back and forth movements, that is, reciprocating movement in a longitudinal direction of the cutting tools. In a dental handpiece in the past, when an edge portion of a cutting tool is caught by a curved portion of a root canal or the like, the cutting tool does not progress further from the caught portion and stays there, therefore, only a head of the dental handpiece relatively goes up and down, which causes the root canal not to be cut at all.
Further, when the cutting tool is forced to be depressed, it is cut into a wall of the root canal and fixed thereto, therefore, the cutting tool does not move any more, which causes a vicious circle in which only the dental handpiece to be liable to go up and down. If the edge portion of the cutting tool is cut into the wall of the root canal, the edge portion may be damaged or broken. Still further, when only the dental handpiece goes up and down, a hand holding the handpiece vibrates, so that it becomes difficult to maintain the posture for cutting operation, which may cause an abuse such as the shift of the position to be processed.
Further, in case that the cutting tool reaches a portion near a root as the cutting operation proceeds, the cutting operation at the portion also mainly relies on the feeling of a dentist, so that the cutting tool may pierce the apical foramen of the dental root. If the cutting tool pierces the apical foramen of the dental root, osteomyelitis or periodontitis may occur, therefore, the phenomenon must be avoided.
In a dental handpiece rotating only one direction, that is, either normal or reverse direction, or reciprocally rotating both normal and reverse directions, that is, so called twist handpiece, a spiral cutting edge portion of the cutting tool proceeds while rotating by a driving source such as a motor, and the force of the driving source causes the edge portion of the cutting tool to be cut into a wall of a root canal and to rapidly be drawn toward a apical foramen of the dental root. As a result, there is a fear that the cutting tool pierces the apical foramen of the dental root or the cutting tool is damaged or broken since the edge portion is excessively cut into the wall of the root canal and locked thereto. Besides, the cutting tool forcibly proceeds, so that smooth root canal cannot be formed, and the surface of the wall is spirally scratched (tapping phenomenon), resulting in a rough surface of the wall.
To prevent the above phenomenon, in the rotational cutting, the moment that the edge portion is cut into the wall the edge portion must repeatedly be raised so as not to pierce the root apex and not to be locked, which forces excessive moral pressure upon a dentist. In a dental handpiece incorporating the rotation and the back and forth movements, the above-mentioned problems will be overlapped.
It is therefore an object of the present invention to provide a dental handpiece stably cutting a wall of a root canal without a fear of piercing an apical foramen of the dental root. To accomplish the above objective, a dental handpiece according to the present invention comprises: means for holding a tool cutting a tooth to be cured; and a support for setting the cutting tool at a desired position relative to the tooth to be cured.
In the above dental handpiece, the length of the support may be changeable by stages; the holding means may comprise a head of the dental handpiece, and a plurality of supports with different lengths may be removably mounted to the head; the support can stand on a head of the dental handpiece; length of the support projecting from the head is changeable; the support is to separately be formed from the dental handpiece so as to be removably mounted thereto; the support may have a stopper; and the support can abut with a tooth to be cured or an appropriate portion near the tooth.
In case of a rotation type dental handpiece, when a cutting tool driven by the handpiece cuts a root canal, a support is mounted to the handpiece, and the support abuts with a tooth to be cured or an appropriated portion near the tooth, which allows load applied to the cutting tool to be dispersed since the support receives a part of the load. In addition, the posture of the handpiece in cutting operation can be maintained to conduct stable cutting operation.
In case of a back and forth movements type dental handpiece, force applied to a cutting tool is transmitted to a support, and there is no fear of engagement or locking of the cutting tool, which allows continuously stable cutting operation. And, the up and down movements of the head accompanied by the engagement or locking of the cutting tool can be mitigated, and the movement of a hand is also prevented.
In both rotation type and back and forth movements type dental handpieces, the engagement and breakage of the cutting tool are prevented, therefore, wear of the cutting tool can be decreased so that the life thereof will become long; and the number of works for replacing the cutting tool is also decreased to shorten a period of time for cure.